Aerogel is a synthetic porous ultralight material and advanced material of transparent ultra-low density having a porosity of 90-99.8% and specific surface area of several hundreds to a maximum of 1500 m2/g. The aerogel, originally manufactured by Steven Kistler in 1931, has been prepared by replacing liquid with gas without causing contraction in the state of being gel. It is also called frozen smoke, solid smoke, solid air or blue smoke since it disperses light in the gel even though it is semi-transparent.
Such a porous aerogel can be widely used for manufacturing ultra-low dielectric material, a catalyst, a carrier of the catalyst, an insulating material, electrode material, and sound-proof material. In particular, silica aerogel is expected to be useful as a transparent insulating material due to its high translucency and low thermal conductivity, and also has a high potential as a superior insulating material for refrigerators and window insulation material of aircraft, spacecraft, etc. This remarkable thermal insulation of the aerogel is caused by its ability to neutralize three ways of heat transfer such as convection, conduction, and radiation.
Aerogel can be made hydrophobic by chemical treatment, in order to prevent structural changes such as shrinkage and decomposition which can occur when absorbing water. In addition, if the inner part of the aerogel is made hydrophobic, waterjet cutting procedure also becomes possible in spite of generation of rather deep crack due to its hydrophobicity.
Recently, such porous structure and hydrophobicity of aerogels have been used to absorb hydrophobic material. Researchers in New Jersey Institute of Technology and Arizona State University in the US reported that aerogel functions like sponge to remove oil from waste water, so as to effectively absorb oil spilled into the environment. Also Mercouri Kanatzidis and his colleagues of Northwestern University of Illinois have used aerogel to absorb heavy metals contained in effluents from the polluted industrial area.
On the other hand, the most conventional way to separate specific oil-soluble and water-soluble substances from natural material is using solvents. To separate and purify oil-soluble material, an organic solvent extraction method is used wherein nonpolar (oil-soluble) solvent such as ether, benzene, or benzol can be used. Though such a nonpolar solvent is very efficient for separating hydrophobic material, it causes symptoms such as headache, dizziness, excitement, nausea, vomiting, drowsiness, etc. And long-term exposal thereto may lead severe damage to the body, like disorders in central nervous system and blood cancer.
In addition to the fact that efficient nonpolar solvent should be cautiously treated due to strong inflammability, most of the nonpolar solvents are classified as carcinogen. Accordingly, the process using such a solvent should be taken place out of GMP (Good Manufacturing Practice) facility. The GMP is a certificate acknowledging an excellent food and pharmaceutical manufacturing and quality control system, which is a systematic standard for the production and quality management throughout the whole process related to the structure of the production facilities, purchase of raw materials, production, packaging and shipment with an aim to produce safe and high-quality food and pharmaceuticals. In the US and European countries, the GMP is widely applied as a standard for guaranteeing that food and pharmaceuticals are produced in conformity with the prescribed rules in terms of safety, identity, strength, quality, purity, etc. Considering this, it is necessary to comply with the regulations and standard of the GMP when dealing with material directly affecting the human body such as pharmaceuticals, food, etc.
Currently, the extraction process is separated into two stages; the initial stage of material purification is taken place outside the GMP facility and the following stage is held in the GMP facility. As a result, not only does it cost a lot of production fee, it takes more time to complete the procedure due to the division of the process. Accordingly, to make it possible to perform the entire raw material extraction procedure in the GMP facility, a physical process that can replace the organic chemical extraction purification method is required to achieve a stable, efficient, economic extraction procedure.